Electrocution is injury or death that occurs because of electrical shock. If birds sitting on a wire are not getting electrocuted, this means they are not getting shocked by electricity. Essentially, this means that the electricity is able to pass through the birds without damaging them. Electricity works via electrons flowing through conductors. If a bird is able to sit on an electrical wire, it means that the bird is not a good conductor of electricity.
Birds are able to sit on electrical power lines because the electrical current essentially ignores the bird's presence and continues to travel through the wire. A bird's body is not a good conductor of electricity. Electricity, similar to water, flows using the least amount of resistance possible. In electrical power lines, electricity flows along copper wires. Copper is an excellent conductor of electricity in that it allows electricity to flow easily along its surface. A bird, on the other hand, is made of cells and tissues. These cells and tissues do not provide the electricity in the wire with an easier route to travel than the one it is already on. Because a bird's body is not a good conductor of electricity, the electricity essentially ignores the bird on the wire and continues to travel along the copper wiring to its destination.
While birds may sit on the wires of power lines and essentially be safe, they will not be so lucky if they happen to touch the wire and certain other objects at the same time. If the second object is an electrical grounding wire or a second wire carrying another voltage, the voltage difference causes a current flow through the bird between the two wires. Electricity travels from a place of high voltage to low voltage, just as water travels from high elevation to low elevation. A bird, or any living thing, that touches a wire (where electricity is moving from high voltage to low voltage) and also touches a grounded metal object (a place with no voltage) creates a path that allows the electricity to travel through that body and into the place with no voltage. When electricity travels through a body in this fashion, electrocution takes place, and the bird can die.
